Thread-cutting device for straight bar knitting machines



P. DHONDT 3,369,380

THREAD-CUTTING DEVICE FOR STRAIGHT BAR KNITTING MACHINES Feb. 20, 1968 2 Sheets-Sheet 1 Filed Oct. 21., 1965 INVENTOR. R D/vonc/f ATTOKNE-ESS P. DHONDT Feb. 20, 1968 THREAD-CUTTING DEVICE FOR STRAIGHT BAR KNITTING MACHINES 2 Sheets-Sheet 2 Filed Oct. El. 1965 I NVENTOR. P. Dhoncli' BY Sham n;

AT To mNEfls United States Patent Ofifice ABSTRACT OF THE DISCLOSURE Mechanism for severing end threads of completed fabric panels produced by a plurality of side by side units of a knitting machine comprising an axially movable rod common to all units carrying thread-lowering and electric resistance thread-cutting devices for each unit, a cooperating axially movable rod common to all units for actuating said thread-lowering devices for severing of the threads, and control means for actuating said rods after knitting of several rows of new fabric panels.

The present invention concerns a thread-cutting device particularly intended for knitting machines belonging to the type consisting of a plurality of knitting units arranged side-by-side, which units are controlled by a common programmation device.

Devices of this kind have already been suggested, either belonging to the mechanical type or to the pneumatic type, and designed for being mounted in front of the needle-bed of each knitting head of the machine. These knOWn devices have however the disadvantage either of being very bulky and delicate to operate, or of requiring to be individually preadjusted in accordance with the width between selvedges of the knitted fabric.

A first object of the present invention is to provide a thread-cutter which is extremely simple, of small bulk and the operation of which does not require any setting by hand, whatever may be the number of knitted panels and the width between selvedges thereof.

Another object of the present invention is to provide a thread-cutter designed so as to hold the last thread of a knitted fabric which falls from a needle-bed until the carriers for the following knitting work have been fit into place either by hand or automatically, and until two or three rows of the new panel have been knitted, the thread being cut only after this last operation has been performed.

For explaining more clearly the characteristic features and advantages of the present invention, a particular embodiment of the latter shall now be described by way of illustration and without implying any restriction with reference to the appended drawings of which:

FIGURE 1 is a diagrammatic partial plan view of a knitting machine equipped with the device according to the present invention;

FIGURE 2 is a diagrammatic partial front view of the device conforming to the present invention;

FIGURE 3 illustrates, on an enlarged scale, the thread lowering system which is part of the device according to the present invention;

FIGURE 4 is a section along the line IV-IV of FIGURE 2, in which the thread lowering system is in the low position;

FIGURE 5 is a diagrammatic perspective view of a controlling part of the device conforming to the present invention;

FIGURE 6 illustrates the wiring diagram of the device conforming to the present invention.

3,369,380 Patented Feb. 20, 1968 In the example of the embodiment considered herein, the knitting machine belongs to the type comprising a plurality of knitting units 1 of which each one is fitted with a needle-bed illustrated diagrammatically at 2, whereby the machine may comprise 8, 12, 16- or 20 knitting units. These units are controlled by a common programmation device making use of punched cards for instance; the knitting width on said units is adjusted by way of common selvedge blocks, all such devices being well known in the art and therefore not illustrated in the appended drawings.

The thread-cutter conforming to the present invention is common to all knitting units 1 and mainly consists of a hollow rod 3 extending over the whole width of the frame and in front of said needle-beds 2. This hollow rod 3 is guided by bearings mounted in uprights 4 of the knitting frame body. At one of its ends, this hollow rod 3 carries a rack 5 driven by a pinion 6 of a reduction device 7 which in turn is driven by an electric motor 8 fastened to some fixed part of the knitting machine. This motor 8 preferably belongs to a type which can stop very suddenly.

Said hollow rod 3 carries, in front of each needle-bed 2 a support 9 provided with an electric resistance 10 and, next to each support 9, a support 11 fitted with a lateral pivot 12. Each one of said pivots l2 accommodates a bell crank lever 13 of the thread-lowering device. The upper end of each one of said bell crank levers 13 is provided with a head 14 of which the cross-section is a V with the opening pointing toward said support 9. The lower ends 15 of each one of the aforesaid levers 13 are connected by a common rod 16 of which the one end is fastened to the armature 17 of a solenoid 18 which in turn is fastened to the end of said rack 5 while its other end is connected to a fixed part 19 of the knitting machine by means of a return spring 20. Said hollow rod 3 also carries a little block 21 and another little block 22 for operating the microswitches 23 and 24, respectively. Microswitch 23 is fastened end-on to a support 25 connected to the main lefthand selvedge carrier 25' while microswitch 24 is carried by a slide 26 which guides said rack 5. Knitting machines of this type are provided with a pair of so-called selvedge blocks the spacing of which determines the width of the fabric being knitted and the travel of the thread feeders. Blocks 21 and 22 are both fixed to the rod 3, the former being located upon the rod in a position between the two selvedge blocks and the latter, as shown-in FIG. 2. The reason why the block 21 is positioned in this location is that the place where the end thread is to be caught by the head 14 varies according to the width of the knitted fabric.

As illustrated in FIGURE 6, the device conforming to the present invention comprises moreover a switch 27 operated by the programmation device of the machine and intended for thread-cutting device, whereby a timing device 28 controls a switch 29 which in turn controls either the excitation of a transformer 30, or the reverse rotation of motor 8 via the reversal switch 31 comprising a forward contact 32 and a rear contact 33; and, finally, the relays 34-35 and 36.

The device which has been described above operates in the following manner: at the end of the work, the knitted fabrics drop from the needle-beds 2 and are pulled forward with their respective end-threads. The attendant then fits into place, either by hand or automatically, the carriers for the following set-up. As soon as the knitting machine has been set, a perforation of the punched card of the machine programmation device sends an impulse by the switch 27 toward the forward contact 32 of the reversal switch 31, which causes rack 5 to be displaced to the right (FIGURE 2). Said conproviding impulses for operating the tact 32 is kept under tension by microswitch 23. Simultaneously, the solenoid 1748 is excited and pulls the rod 16, the result of which is to lift the levers 13 which are thereby simultaneously displaced to the right (FI URE 2) by rack 5. By means of this displacement, the open head 14 of each one of said levers 13 catches and draws along the end-thread of the corresponding knitted fabric. The displacement to the right of the hollow rod 3 is such that block 21 actuates the microswitch 23 carried by the support 25 attached to the carrier of the machine. When the microswitch 23 is operated, the circuit toward contact 32 is broken, so that the current in solenoid 17-18 is cut-off and relay 34 is switched on, with the result that motor 8 stops short and stops the motion of rack 5, while said rod 16 is pulled back by its return spring 20 in such manner that the levers 13 fold back while their heads 14 hold the threads against the resistances 10. At this stage, the switching on of relay 34 has no effect.

Two or three rows after the knitting of the new panel has been resumed, a second perforation of the punched card of the programmation device of the machine sends a new impulse to switch 27, which causes the timing device 28 to be operated over the relays 34-35 and 36 and hence also transformer 30 excited via switch 29. The resistances 10 are then brought to a red heat during the time needed for severing said end-threads. After this time has elapsed, the timing device 28 reverses switch 29, to cut off the current toward transformer 30 and to close directly the circuit of reversal switch 31 rearwardly, whereby the latter is kept under tension by relay 34. As soon as the rear contact 33 has been switched on, motor 8 sets rack into motion toward its starting position. Microswitch 23 is released and relay 34 is cut out. At the same time, relay 36 operates, which breaks the holding circuit toward relay 34. The motor 8 goes on turning until the hollow rod 3 carrying the resistances has come back to its starting point position in which the block 22 operates microswitch 24, which brings the motor 8 to a standstill. The thread-cutting device has thus come back into its initial position and is ready to operate again in the same way. It is thus apparent that when the switch 27, which is of the pushbutton type, is closed at the beginning of the cutting cycle, it will close the circuit of the contact 32 which is displaced to the left (looking in the direction of FIG. 6). When so displaced, the contact 32 is kept energized by the circuit controlled by the micro-switch 23 so long as the micro-switch is kept in the position shown in FIG. 6, namely, so long as it is not engaged by the block 21. Actuation of the micro-switch 23 will actuate, among others, the relay 34, so that when the push-button switch 27 is again actuated, the circuit which includes the timing device 28, will be energized. This second closing of the switch 27 has no efiect upon the reversal switch 31 due to the positions of the relay 34 and microswitch 23.

A thread-cutter according to the present invention has the particular advantage to occupy very little room in the front of each needle-bed. In fact, it is only said hollow rod, the parts carried by thelatter and the rod controlling the thread lowering levers which must find room between said needle-beds and the winding-up device of the knitted fabric, as the other constituent elements of the threadcutting device can be placed in any convenient part of the knitting machine. So for instance, the major part of the electric control circuit of the thread-cutter can be assembled in a box or casket fastened at the rear of the frame whereby the box in question can for instance contain said timing device, the various relays and said contacts.

It is obvious that the present invention is in no Way limited to the example of embodiment described above and illustrated by the appended drawings, and that all sorts of changes may be effected both in connection with the shape and with respect to the relative dispositions of each one of the constituent parts of the thread-cutting device conforming to the present invention, without exceeding the scope of the latter.

What I claim is:

1. A thread-cutting apparatus for knitting machines of the type having a plurality of knitting units arranged endon, said apparatus comprising an axially mobile part extending in front of all of said knitting units, a separate thread lowering device located upon said part in front of each knitting unit, a separate thread-cutting device located upon said part in front of each knitting unit, means axially displacing said part to move said thread lowering devices into contact with the threads to be cut, means common to all said thread-lowering devices for operating the latter to bring the threads to be cut within reach of said thread-cutting devices, and means controlling said thread-cutting devices after said thread lowering devices have moved said threads in contact therewith.

2. Thread-cutting apparatus according to claim 1, wherein said axially mobile part comprises a hollow rod, the thread-cutting devices comprising electric resistances which can be heated to incandescence.

3. Thread-cutting apparatus according to claim 2, wherein said means for positioning said hollow rod comprises an electric motor carried by the machine, a rack connected to an end of said rod, a transmission connecting said motor with said rack, a reversal contact, a micro-switch tensioning said contact and operated by said rack at the end of its stroke.

4. Thread-cutting apparatus according to claim 2, comprising a timing device for controlling the heating of the electric resistances.

5. Thread-cutting apparatus according to claim 1, wherein said means common to all thread-lowering devices for operating the latter comprises a common rod connected to the lower end of each thread-lowering device, a solenoid and a return spring, one end of said rod being connected to the armature of said solenoid, while the other end is acted upon by said return spring.

6. Thread-cutting apparatus according to claim 5, wherein each one of the thread-lowering devices comprises a bell crank lever of which the upper end has a head of V cross-section.

References Cited UNITED STATES PATENTS 2,432,110 12/1947 Lambach 66-145 2,674,866 4/1954 Dyjak 66-145 FOREIGN PATENTS 1,267,525 6/1961 France.

ROBERT R. MACKEY, Primary Examiner, 

